1. Field
The present disclosure relates generally to power inverters, and more particularly, to modular plug-and-play power inverters for a renewable energy power source.
2. Related Art
Renewable energy generators, such as solar panels, often produce an output in the form of direct current (DC) electric power. However, many loads require power in the form of an alternating current (AC) electric power having a particular frequency and voltage. Thus, in order to use energy produced by a renewable energy generator in, for example, a home, an inverter may used to convert the DC electric power output of the generator into an AC electric power having the desired characteristics.
Generally, renewable energy generators, such as solar panels, produce intermittent, highly variable, DC power outputs with dynamic ranges. This is largely due to the variable nature of the input to the renewable energy generators. For example, the amount of energy generated by a solar panel relies heavily on the amount of sunlight reaching the panel's surface. Since the intensity of sunlight changes constantly throughout the day, the DC power output of the solar panel is also constantly changing. A problem caused by such a dynamic range of input power is reduced efficiency at low power levels. Inverters convert DC power to AC power more efficiently when the input DC power closely matches the optimal power rating of the inverter. Since the DC power output of a renewable energy generator is intermittent and highly variable, current inverters often suffer from efficiency loss due to the fluctuations in the DC power output. Thus, an inverter capable of matching the optimal power rating of the inverter to its DC power input is desired.
Additionally, multiple renewable energy generators are often operated in conjunction, resulting in a power output equal to the sum of the individual generator outputs. However, the number of generators used in one application may vary drastically from the number of generators used in another application or in the same application over time. Due to the unpredictable inversion demands of expandable systems, the selection of a properly rated inverter may be difficult. Current inverters, particularly inverters having a static inversion capacity, are at risk of either being underrated, resulting in wasted power-generating capacity, or overrated, resulting in inefficiency both in power inversion and cost of materials. Even if an inverter adequate for existing inversion demand is selected, a user may find the inverter inadequate for changing needs as additional energy generators are added or removed from a system. Thus, an inverter capable of expanding its inversion capacity by coupling to multiple transformer modules is desired.
Depending on the amount of power generated by a renewable energy generator and the power demands of the generator's user, more power may be produced than can be consumed by the user. In this event, rather than have the excess power go to waste, the user may sell the power to a utility company. For example, a home owner having solar panels fixed to the roof of his/her home may sell the power generated by the solar panels to the local electric utility. In return, the home owner may receive a credit on his/her next electricity bill or receive some other form of compensation. Some current inverters may be capable of calculating, recording, and communicating the amount of power delivered to the utility company. However, the cost of replicating such communication devices, memory chips, system control, and data logging capability within existing scalable systems such as AC Modules, makes the cost of such systems prohibitive for many users. Thus, an inverter capable of separating costly “intelligent” features from inversion capacity features is desired.
When used to power a particular location, current generator systems may suffer from “islanding.” Islanding refers to the condition whereby a generator continues to power a location even though power from an electric utility is no longer present. This creates a dangerous situation as others may not be aware of the generator and may be harmed by the generated power. For example, utility workers may assume that a building is un-powered and may be electrocuted while working with the building's electrical wires. Thus, an inverter including safety measures for safely disconnecting the generator from the load in the event of a loss of electric utility power is desired.
Within the solar field, AC Modules provide one solution to scalability; however, they output a high-voltage, making them unsafe for handling by unskilled laborers and requiring expensive electricians for the installation and preparation of such systems. This also restricts the inverter to a single location. Therefore, a portable inverter operable to easily connect to a household AC power network and providing a low-voltage solution to inverter scalability is desired.